This invention pertains generally to radar systems, and particularly to any type of such systems that uses high data rate anti-radiation missile decoys.
It is well known in the art that an anti-radiation missile (ARM) is adapted to home on radio frequency (R.F.) signals radiated so that an explosive charge carried by such a missile may destroy a radar. To accomplish such homing, the guidance system in an ARM missile may be designed to lock onto the leading or trailing edge of radar interrogating pulses, as well as midpulse samples of such pulses. It is therefore desirable that, in order to increase the chance of survivability of a radar attacked by an ARM missile, decoys located in the vicinity of the radar be actuated to generate R.F. signals to cause the guidance system in an attacking ARM missile to home on an apparent source spaced from the radar. Thus, R.F. signals from the decoys are synchronized with the interrogating signals from the radar so that the R.F. signals from the decoys produce pulses overlapping (in power and time) the interrogating pulses produced by sidelobes of the antenna in the radar. Consequently, the guidance system in an attacking ARM missile is precluded from using the leading or trailing edges or midpulse samples of the interrogating pulses to derive guidance commands. Further, the decoys are caused to "blink". That is to say, only one of the decoys is allowed to be operative to overlap a given interrogating pulse. As a result of such "blinking" the aim point of the ARM is caused to wander, thereby preventing the ARM from homing on the radar or any one of the decoys.
A decoy capable of producing overlapping pulses with sufficiently high power levels usually comprises a master oscillator-power amplifier configuration wherein a traveling wave tube (TWT) chain is driven by a frequency agile exciter. While such a configuration may be operable with a relatively high duty cycle, there are several deficiencies that make use of such a decoy unattractive. Firstly, the physical size of TWT is large for the purpose, and cooling means are required. Further, a high voltage power supply that is quite complex is required because a grid modulator, a tube body supply and one or more depressed collector supplies must be provided. Hence, a simpler and less expensive alternative approach is desirable.
A magnetron oscillator as an R.F. energy source is less expensive than a TWT in a master oscillator-power amplifier configuration for a decoy. However, any known type of magnetron oscillator, although capable of producing covering pulses with the requisite peak power levels, is presently limited to relatively low duty cycles, i.e., a maximum of one percent. Therefore, if the duty cycle of interrogating pulses transmitted from a radar is greater than one percent, a magnetron oscillator cannot, by itself, produce covering pulses having a length sufficiently long to mask the interrogating pulses.